following is my frame buffer obj testing code:
got confused why the outputs are different? can anybody give a clue? tks alot.
// FBO1.cpp : Defines the entry point for the console application.
//
#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include <GL/glew.h>
#include <GL/glut.h>
int main(int argc, char argv) {
// declare texture size, the actual data will be a vector
// of size texSizetexSize4
int texWidth = 2;
int texHeight = 4;
// create test data
unsigned char data = (unsigned char)malloc(texWidthtexHeightsizeof(unsigned char));
unsigned char* result = (unsigned char*)malloc(4texWidthtexHeightsizeof(unsigned char));
for (int i=0; i<texWidthtexHeight; i++)
data[i] = (unsigned char)(i+1);
// set up glut to get valid GL context and
// get extension entry points
glutInit (&argc, argv);
glutCreateWindow(“TEST1”);
glewInit();
// viewport transform for 1:1 pixel=texel=data mapping
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,texWidth,0.0,texHeight);
glMatrixMode(GL_MODELVIEW);
glLoadIdentity();
glViewport(0,0,texWidth,texHeight);
// create FBO and bind it (that is, use offscreen render target)
GLuint fb;
glGenFramebuffersEXT(1,&fb);
glBindFramebufferEXT(GL_FRAMEBUFFER_EXT,fb);
// create texture
GLuint tex;
glGenTextures (1, &tex);
glBindTexture(GL_TEXTURE_RECTANGLE_ARB,tex);
// set texture parameters
glTexParameteri(GL_TEXTURE_RECTANGLE_ARB,
GL_TEXTURE_MIN_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_RECTANGLE_ARB,
GL_TEXTURE_MAG_FILTER, GL_NEAREST);
glTexParameteri(GL_TEXTURE_RECTANGLE_ARB,
GL_TEXTURE_WRAP_S, GL_CLAMP);
glTexParameteri(GL_TEXTURE_RECTANGLE_ARB,
GL_TEXTURE_WRAP_T, GL_CLAMP);
// define texture with floating point format
glTexImage2D(GL_TEXTURE_RECTANGLE_ARB,0,GL_RGBA,
texWidth,texHeight,0,GL_LUMINANCE,GL_UNSIGNED_BYTE,0);
// attach texture
glFramebufferTexture2DEXT(GL_FRAMEBUFFER_EXT,
GL_COLOR_ATTACHMENT0_EXT,
GL_TEXTURE_RECTANGLE_ARB,tex,0);
GLenum status = glCheckFramebufferStatusEXT(GL_FRAMEBUFFER_EXT);
assert(status == GL_FRAMEBUFFER_COMPLETE_EXT);
// transfer data to texture
glTexSubImage2D(GL_TEXTURE_RECTANGLE_ARB,0,0,0,texWidth,texHeight,
GL_LUMINANCE,GL_UNSIGNED_BYTE,data);
// and read back
glReadBuffer(GL_COLOR_ATTACHMENT0_EXT);
glReadPixels(0, 0, texWidth, texHeight,GL_LUMINANCE,GL_UNSIGNED_BYTE,result);
// print out results
printf("Data before roundtrip:
“);
for (int i=0; i<texWidthtexHeight; i++)
printf("%u
",data[i]);
printf("Data after roundtrip:
");
for (int i=0; i<texWidthtexHeight; i++)
printf(”%u
",result[i]);
// clean up
free(data);
free(result);
glDeleteFramebuffersEXT (1,&fb);
glDeleteTextures (1,&tex);
return 0;
}